Low-fuming galvanizing fluxes

ABSTRACT

Low-fuming galvanizing fluxes are provided which exhibit superior fluxing activity and which contain zinc chloride or zinc bromide and a zinc phosphate or zinc phosphite as the active agents. Galvanizing fluxes of this invention may also contain a small amount of a foaming agent and the chloride or bromide of sodium, potassium, lithium, magnesium and/or calcium.

United States Patent [191 Chay LOW-FUMING GALVANIZING FLUXES [75] Inventor: Dong M. Chay, Wilmington, Del.

[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

22 Filed: Apr. 13, 1973 211 App]. No.: 350,797

Related US. Application Data [63] Continuationin-part of Ser. No. 316,404, Dec. 18,

1972, abandoned.

2,106,982 2/1938 Kepfer 148/25 X 1 June 11, 1974 2,473,579 6/1949 Eubank 148/23 2,488,246 1 H1949 Stureck et a1. 2114/55 R 2,511,952 6/1950 Stareck et ul. i 204/55 R X 2,515,488 7/1950 Boiler et a1. [48/26 X 2,793,965 5/1957 Myers at 211.... 117/131 X 2,811,484 10/1957 Long 204/55 R 2,940,870 6/1960 Baldwin 75/96 X 3,030,242 4/1962 Gieselman et a1. 117/131 X FOREIGN PATENTS OR APPLICATIONS 751,636 7/1956 Great Britain 148/26 Primary ExaminerA. B. Curtis Assistant ExaminerThomas A. Waltz [57] ABSTRACT Low-fuming galvanizing fluxes are provided which exhibit superior fluxing activity and which contain zinc chloride or zinc bromide and a zinc phosphate or zinc phosphite as the active agents. Galvanizing fluxes of this invention may also contain a small amount of a foaming agent and the chloride or bromide of sodium, potassium, lithium, magnesium and/or calcium.

14 Claims, N0 Drawings LOW-FUMING GALVANIZING FLUXES CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application Ser. No. 316,404 tiled Dec. 18, 1972,

now abandoned.

BACKGROUND OF THE INVENTION It is well known that a top flux and possibly even a preflux is employed in the galvanizing of metal articles. Such fluxes traditionally contained ammonium chloride or some ammonium halide at a high concentration (greater than 9 percent) to aid in the effective cleaning and wetting of the surface of the article to be galvanized. In addition to cleaning the surface to be galvanized, such expedients promoted the fluidity of the flux and effectively stirred the flux mixture via sublimation or the evolution of decomposition products. The use of fluxes containing such agents allows a continuous, adherent film of zinc, substantially free of pinholes and other imperfections to be deposited on the surface of the substrate tobe galvanized.

Many prior art fluxes also contain substantial amounts of zinc chloride which generally acts as a carrier and in so doing forms a double salt with the ammonium halide'in situ with the evolution of ammonia. As a consequence, ammonium halide containing fluxes which also contain zinc chloride have much greater stability and are easier to use. I

Despite the fact that fluxes containing high concentrations of the ammonium halide compounds are unquestionably effective, severe disadvantages are encountered in the use of such materials. The tendency of the ammonium compounds either to sublime or to yield decomposition products which in turn sublime is highly objectionable. The sublimation and decomposition products evolve as thick, white, noxious fumes which are pollutants.

Nevertheless, flux formulations having high activity levels and a long use life are not obtainable if little or no ammonium chloride is contained in the formulation. Simply lowering the concentration of the ammonium compound not only reduces the fuming and dross formation but also the efficiency of the reaction and dispersion of the undesirable metal oxides with the active ingredients in the flux mixture. Substrates which were less than well cleaned and pickled were found to have uncoated spots. In addition, the top flux quickly thickened and'became viscous and flux stains and inclusions were found to be much more prevalent.

In order to meet and overcome suchproblems various alternatives have been proposed. For example, galvanizing fluxes in which a fluoride salt is employed have been disclosed in'U.S. Pat. No. 3,244,55I,issued' to Sidney-M. Heins on Apr. 5, 1966. Low fuming fluxes have been proposed in which various frothing agents are employed such as, for example, In U.S. Pat. No.

2,940,870 issuedto Allen T. Baldwin o'nJune 14, 1960 and U.S. Pat. No. 2,473,580 issued to' Lowell D. Eubank et al., on June 21, 1949. As discussedhereinbefore, fluxes which are low fuming by virtue of a low concentration of ammonium compounds have been less effective, particularly as measured by commercial standards.

SUMMARY OF THE INVENTION It is now possible to prepare low fuming galvanizing fluxes substantially devoid of the foregoing disadvantages which contain zinc chloride or zinc bromide and a zinc phosphate or zinc phosphite. The galvanizing fluxes of this invention may also contain a small amount of a foaming agent and/or the chloride or bromide salt of sodium, potassium, lithium, magnesium and/or calcium. Small amounts of ammonium halide, preferably ammonium chloride or ammonium bromide, most preferably ammonium chloride may also be used in the fluxes of this invention without the detriment heretofore attendant upon its use.

DETAILED DESCRIPTION OF THE INVENTION In general, the unique fluxes of this invention retain their effectiveness notwithstanding quite broad variation in their composition. In every instance, however, the fluxes of this invention must contain either a zinc phosphate or zinc phosphite and zinc chloride or zinc bromide as an adjuvant, preferably zinc chloride. While the amounts of these essential agents in the flux composition may be varied widely, preferably from about to about parts by weight of the zinc chloride or bromide and about 3 to about 15 parts by weight of the zinc phosphate or zinc phosphite are employed.

In the practice of this invention, it is preferred that the zinc phosphate is a zinc orthophosphate, a zinc triphosphate, a zinc metaphosphate, a zinc pyrophosphate or a zinc ammonium phosphate compound. Examples of some such suitablephosphates include ZN2P207 Any suitable zinc phosphite may also be employed,

such as for example While zinc chloride may be used interchangeably with zinc bromide with substantially similar results, one may also employ in addition to either of these two agents a chloride or bromide of sodium, potassium, lithium, magnesium and/or calcium. In such a case, the galvanizing flux will contain preferably from 80 to 100 parts by weight of the desired admixture. The only limitation to be observed in using such admixtures is that the amounts of the chloride or bromide salts of sodium, potassium, lithium, magnesium and/or calcium which are employed must be such that an admixture of the zinc chloride or zinc bromide with one or more of the salts will be completely molten at the operatingtemperature of the bath. Preferably such compositions contain from 20 to 60 parts by weight of the chloride or bromide salt of sodium, potassium, lithium, magnesium and/or calcium and 40 to 80 parts by weight of the zinc chloride and/or zinc bromide and are completely molten at temperatures of from about420 to 425C, most preferably 421C.

In one variation of this invention, small amounts of a foaming agent or surfactant or stabilizer may be employed in the flux mixture. Generally, concentrations of from to about 0.5 part by weight of the foaming agent are used. Any suitable foaming agent which acts to stadiamino naphthalene, 1,3, 6-hexane triamine, propylene triamine, 1,2,3-benzene triamine, 2,6-diamino pyridine and the like and mixtures thereof.

In another embodiment of this invention, a small amount of an ammonium halide such as ammonium chloride and/or ammonium bromide and the like, preferably ammonium chloride is used but only at concentrations of from 0 up to a maximum of about 5 parts by weight. The decomposition rate of the ammonium halide at such low concentrations is very slow and only a negligible amount of decomposition takes place at any given time. The effectiveness of the ammonium halide at such low concentrations is primarily limited to the initiation of' the activity of the flux at the start-up of v fluxing operations after which the zinc phosphate or zinc phosphite compound takes overas the active ingredient.

While each of the several embodiments of this invention has been discussed individually, it is to be understood that each such embodiment is not exclusive of any other. Accordingly, any of the various embodiments of this invention may be combined in any given ates efficiently and effectively without the noxious fumes of commercial ammonium chloride containing fluxes and without the less than excellent results which attend the use of prior art fluxes containing no ammonium chloride or else only low concentrations of the ammonium compound.

The fluxes of this invention are advantageously em ployed whether the bath metal is zinc, as in conventional galvanizing, a zinc alloy or even an alloy such as Su-Pb which is used in terne coatingl In addition, articles of any desired shape can be coated with the bath metal using the fluxes'of this invention as discussed, for example, in Hat-Dip Galvanizing Practice, William H. S'powers, Jr., The Penton Publishing Company, Cleveland, Ohio, 1938, pp. 32-70. The instant fluxes are most advantageous for the coating of ferrous and tin articles.

The invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight, unless otherwise indicated.

1. The first method utilizes a Brookfield viscometer, model LVT, modified to measure viscosities of fluxes at elevated temperatures by the insertion of an adaptor between the spindles and the meter to provide thermal insulation. The adaptor which is tubular in shape, constructed of heat resistant cloth reinforced phenolic resin, measures 1% L X /2 OD X 54; lDand weighs 4.2

' EXIXMPLES 1-11 Amounts of all components in parts by weight) Viscosity Summary Table of Examples Example ZnCl NaCl KCl NH ZnPO n;1(PO,) ,'2H O Zn;1(PO NH,CI PET" Viscosity l 100 5 I cps 2 99 5 l 0.3 5 sec 3 79 5 1 0.2 20 sec 4 I00 5 5 0.3 2 sec 5 I00 5 5 5 sec- 6 I00 l5 5 0 l 20sec 7 99 3 25'5 cps '8 100 3 3 0.2 S sec 9 )9 31 23 7 25 cps It) 100' I 3i 23 7 5 0.l 2 sec 1 l 90 20 7 3 0.1 5 sec cps units indicate measurement by Method l; sec (seconds) units indicate measurement by Method 2 flux composition as desired, or all of the embodiments grams. The adaptor is pushed over the serrated tip of may be employed simultaneously as desired. No matter how the flux compositions of this invention are varied; it has been found that the resulting composition operthe spindle and fastened thereto by a set screw. The other end of the adaptor is similarly attached to the meter shaft so that metal to metal contact between the spindle and shaft is prevented A thin asbestos sheet is also placed between the spindle-guard bracket and the meter to provide further thermal insulation to the meter.

In measuring flux viscosity, the spindle is submerged V in molten flux maintained at a temperature of 355C.

for two minutes before the reading is taken. This allows for temperature equilibration between the molten flux and the spindle. The viscometer is cleaned and checked against a standard solution of 95 percent glyeerine and 5 percent water at a temperature of 30C. after each measurement of flux viscosity.

2. The second method is a semi-qualitative one in which a 3 inch wide steel spatula is inserted into a layer of molten flux floating on the surface of a zinc bath maintained at a temperature of 455C. When the tip of the spatula reaches the surface of the molten zinc, the

spatula is swept quickly through the molten flux layer,

thus separating it by a three inch swath in which the surface of the molten zinc is exposed. The time required for the flux to coalesce across the three inch swath is measured. The time required for coalescence increases with increased viscosity of the flux.

EVALUATION A galvanizing kettle of about X 10 X l0 inch size containing molten zinc at 455C. is used to evaluate the fluxes of Examples A, B and 1-1 l-.'The Prime Western grade zinc is used in the evaluation. Approximately 300 grams of the flux are placed in the kettle which is equipped with a darn dividing the molten zinc surface into two halves. The flux is placed on the surface of one of the halves in one spot from which it melts away to cover that half of the molten zinc surface. All of the flux melts in about 4 minutes. The flux is heated for about 10 minutes longer before galvanizing is begun. I Soft steel coupons are used toevaluate the effectiveness of the flux. Coupons of 3% X 2% X /4 inch in size are first degreased by heating in a solution prepared by dissolving 39 grams of sodium hydroxide, 104 grams of sodium metasilicate and 2.5 grams of a sodium hydrocarbon sulfonate wetting agent in a sufficient amount of water to make 1 gallon solution. After being heated at 88C. for minutes in this solution, the coupons are rinsed and pickled in a 10 percent sulfuric acid solution at 70C. for 20 minutes. After being rinsed with water the coupons are allowed to dry.

When the coupons are completely dry, they are lowered slowly into the molten zinc through the flux which has been heated for l0 minutes on the surface of the molten zinc at 455C. The coupons are held in thezinc for 90 seconds before being withdrawn through the molten zinc surface which does not contain a layer of flux and they are then cooled with water.

COMPARATIVE EXAMPLES In order to provide a comparative basis against which the performance of the fluxes of this invention can be measured. two flux compositions areprepared. Composition A is a regular commercial flux heretofore generally employed in the prior art. Composition B is a low fuming flux currently available commercially.

A. About 300 parts of the regular commercial flux containing about 46 percent of zinc chloride and about 54 percent of ammonium chloride are placed on top of molten zinc maintained at a temperature of 455C. as described above. Within about 30 seconds, the flux begins to give off profuse fumes which continue until all of the flux becomes molten. After about five minutes all of the flux is molten and produces a two and one half inch thick layer of foam on the surface of the molten zinc. Fuming decreases slightly.

B. About 300 parts of a commercial low fuming flux containing about 66 percent of zinc chloride, about 20 percent of sodium chloride, about 13 percent of potassium chloride and about 1 percent of ammonium chloride are placed on the surface of molten zinc as described above. The flux fumes slightly during melting. After the flux is molten, however, the fuming is noticeably redu'ced although slight fuming is still visible.

EXAMPLE 1 The molten flux of this example formed a thin, substantially foam free layer on the surface of the molten zinc and fumed only slightly more than low-fuming flux B initially, however, the fuming subsided to level of flux B after about 5 minutes of heating. The coatings obtained using this flux covered the entire surface of the coupon and were smooth, lustrous, uniform and defectfree'. By comparison, coupons galvanized under identical conditions except that no top flux was used remained about 90 percent uncoated.

EXAMPLES 2 AND 3 The molten flux of each example formed a foamy layer about one and one half inches thick on the surface of the molten zinc and fumed'about the same as low-fuming commercial flux B. Each flux permitted the deposition of a galvanized coating over the entire surface of the coupon which was smooth, lustrous, uniformand defect-free.

EXAMPLE 4 EXAMPLE 5 The molten flux formed about a one inch thick foam "layer on the zinc surface. Initially the flux fumed slightly more than flux B although far less than flux A. The fuming subsided to a substantially invisible level after about two minutesof heating. The galvanized coating obtained using-the flux of this example is unifonn, smooth, lustrous and free from defects and covers the entire surface of the coupon.

EXAMPLE 6 The molten flux formed a layer of foam about two inches thick on the molten zinc and fumed only slightly more than flux B in the initial 3 minutes of heating but subsided to about the same level as flux B. The coating obtained when this flux was used covered the-entire surface of the coupon and was smooth, uniform, lustrous and defect-free.

EXAMPLE 7 This flux fumes about the same as flux B during heathaving a few small nodules which, in a commercial operation would not be considered a failure in the coat ing, are obtained using this composition.

EXAMPLE 8 The fluxof this example. fumes no more than flux B throughout the heating and forms a foam layer about one and one half inches thick on the surface of the zinc. A smooth, lustrous, defect-free coating uniform across the entire surface of the coupon is obtained when the flux of this example is employed.

EXAMPLE 9 The flux of this example fumes about the same as flux B throughout the heating and, when molten forms a thin, substantiallyfoam free layer on the zinc surface. Smooth, uniform, lustrous and defect-free coating discernible is obtained across the entire surface of the coupon when this flux is used.

EXAMPLE 10 Upon being heated this flux forms about a two inch thick fluid foam layer and fumes slightly morev than flux B but subsides to the same level after one minute of heating. Galvanized coatings obtained when this flux is used are smooth, lustrous, uniform and defect-free across the entire surface of the coupon.

EXAMPLE 11 This flux fumes about the same as flux B on heating and forms a foam layer about one and one half inches thick. A smooth, lustrous, uniform and defect-free galvanized coating is obtained across the entire surface of the coupon is obtained when the flux of the Example is employed.

It is to understood that any of the components and conditions mentioned as suitable herein can be substituted for its counterpart in the foregoing examples with similar advantageous result and that although the invention has been described in considerable detail in the foregoing, such detail is solely for the purpose of illustration. Variations may be made in the invention by those skilled in the art without departing from the spirit 2. The flux of claim 1 which contains zinc chloride.

3. The flux of claim 2 which contains a zinc orthophosphate, a zinc triphosphate, a zinc metaphosphate, a zinc pyrophosphate or a zinc ammonium phosphate.

4. The flux of claim 1 in which the foaming agent is a polyalcohol, a polyamine, sawdust. flour, the chaff of bran or mixtures thereof.

5. The flux of claim 4 in which the foaming agent is pentaerythritol.

6. The flux of claim 1 which contains the chloride or bromide salt of sodium, potassium, lithium, magnesium, calcium or mixtures thereof in addition to the zinc chloride or zinc bromide.

7. The flux of claim 6 in which the mixture contains from about 20 to about 60 parts by weight of the chloride or bromide salt in admixture with from about 40 to about parts by weight of the zinc chloride or zinc bromide and is molten at a temperature of 421C.

8. The flux of claim 1 which contains ammonium chloride.

9. The flux of claim 1 which contains 80 to parts by weight of zinc chloride, 3 to 15 parts byweight of a zinc phosphate, 0 to 0.5 part by weight of a foaming agent and 0 to 5 parts by weight of ammonium chloride.

10. The flux of claim 9 in which the zinc phosphate 11. In a process for galvanizing an article by passing the article through a molten flux composition and into a bath of zinc, the improvement which comprises passing the article through a flux composition of 80 to 100 parts by weight of zinc chloride or zinc bromide; 3 to 15 parts by weight of a zinc phosphate or zinc phosphite; 0 to 0.5 part by weight of a foaming agent and 0 to 5 parts by weight of ammonium chloride or ammonium bromide.

12. In a bath for galvanizing articles which comprises molten zinc having a molten layer ofa flux composition on the surface thereof, the improvement which co-mprises, as the molten layer of flux, a composition of 80 to 100 parts by weight of zinc chloride or zinc bromide; 3 to 15 parts by weight of a zinc phosphate or Zinc phosphite; 0 to 0.5 part by weight'of a foaming agent and O to 5 parts by weight of ammonium chloride or ammonium bromide.

13. The flux of claim 1 which contains 80 to 100 parts by weight of zinc chloride, 3 to l5 parts by weight ofa zinc phosphite, O to 0.5 part by weight ofa foaming agent and O to 5 parts by weight of ammonium chloride.

14. The flux of claim 13 in which the zinc phosphite is Zn (PO P0405) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,8I L6,l88 Dated June 11, 1974 Inventofls) Dong M. Ch a It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8, line 29, "and" should read or Signed and sealedthis 29th day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer I Commissioner of Patents 

2. The flux of claim 1 which contains zinc chloride.
 3. The flux of claim 2 which contains a zinc orthophosphate, a zinc triphosphate, a zinc metaphosphate, a zinc pyrophosphate or a zinc ammonium phosphate.
 4. The flux of claim 1 in which the foaming agent is a polyalcohol, a polyamine, sawdust, flour, the chaff of bran or mixtures thereof.
 5. The flux of claim 4 in which the foaming agent is pentaerythritol.
 6. The flux of claim 1 which contains the chloride or bromide salt of sodium, potassium, lithium, magnesium, calcium or mixtures thereof in addition to the zinc chloride or zinc bromide.
 7. The flux of claim 6 in which the mixture contains from about 20 to about 60 parts by weight of the chloride or bromide salt in admixture with from about 40 to about 80 parts by weight of the zinc chloride or zinc bromide and is molten at a temperature of 421*C.
 8. The flux of claim 1 which contains ammonium chloride.
 9. The flux of claim 1 which contains 80 to 100 parts by weight of zinc chloride, 3 to 15 parts by weight of a zinc phosphate, 0 to 0.5 part by weight of a foaming agent and 0 to 5 parts by weight of ammonium chloride.
 10. The flux of claim 9 in which the zinc phosphate is Zn3 (PO4)2.2H2O and NH4ZnPO4.
 11. In a process for galvanizing an article by passing the article through a molten flux composition and into a bath of zinc, the improvement which comprises passing the article through a flux composition of 80 to 100 parts by weight of zinc chloride or zinc bromide; 3 to 15 parts by weight of a zinc phosphate or zinc phosphite; 0 to 0.5 part by weight of a foaming agent and 0 to 5 parts by weight of ammonium chloride or ammonium bromide.
 12. In a bath for galvanizing articles which comprises molten zinc having a molten layer of a flux composition on the surface thereof, the improvement which comprises, as the molten layer of flux, a composition of 80 to 100 parts by weight of zinc chloride or zinc bromide; 3 to 15 parts by weight of a zinc phosphate or zinc phosphite; 0 to 0.5 part by weight of a foaming agent and 0 to 5 parts by weight of ammonium chloride or ammonium bromide.
 13. The flux of claim 1 which contains 80 to 100 parts by weight of zinc chloride, 3 to 15 parts by weight of a zinc phosphite, 0 to 0.5 part by weight of a foaming agent and 0 to 5 parts by weight of ammonium chloride.
 14. The flux of claim 13 in which the zinc phosphite is Zn3(PO3)2. 